<?php

declare(strict_types=1);

namespace App\Booking;

/**
 * A span of one day, as minutes from midnight, end-exclusive.
 *
 * Minutes rather than a TIME column on purpose: the end of an all-day booking is 24:00, which
 * TIME cannot express, and half-open integer arithmetic makes the overlap test a plain
 * comparison in both PHP and DQL.
 */
final readonly class TimeRange implements \Stringable
{
    public const DAY_START = 0;
    public const DAY_END = 1440;

    private function __construct(
        public int $startMinute,
        public int $endMinute,
    ) {
        if ($startMinute < self::DAY_START || $endMinute > self::DAY_END) {
            throw new \InvalidArgumentException('Eine Buchung muss innerhalb eines Tages liegen.');
        }

        if ($startMinute >= $endMinute) {
            throw new \InvalidArgumentException('Das Ende muss nach dem Beginn liegen.');
        }
    }

    /**
     * Named wholeDay() and not allDay() on purpose. Twig resolves `range.allDay` by looking for a
     * method literally called `allDay` BEFORE it tries `isAllDay()`, and it does not care that
     * the method is static -- so a factory of that name silently shadows the accessor and every
     * template reads back a fresh all-day range, which is truthy. Keep the two names distinct.
     */
    public static function wholeDay(): self
    {
        return new self(self::DAY_START, self::DAY_END);
    }

    public static function fromMinutes(int $startMinute, int $endMinute): self
    {
        return new self($startMinute, $endMinute);
    }

    /**
     * Reads the clock time off two \DateTime values, ignoring their date part -- which is what
     * the form's TimeType hands over.
     */
    public static function fromTimes(\DateTimeInterface $start, \DateTimeInterface $end): self
    {
        return new self(self::minutesOf($start), self::minutesOf($end));
    }

    /**
     * Parses the board's ?von=&bis= pair. Returns null for anything missing or malformed, so the
     * caller can fall back to the whole day rather than 404 on a hand-edited URL.
     */
    public static function parse(?string $start, ?string $end): ?self
    {
        $hasStart = null !== $start && '' !== $start;
        $hasEnd = null !== $end && '' !== $end;

        if (!$hasStart && !$hasEnd) {
            return null;
        }

        // One-sided input is treated as open to that end of the day, so typing only a start time
        // does something visible instead of silently resetting the board.
        $startMinute = $hasStart ? self::parseClock($start) : self::DAY_START;
        $endMinute = $hasEnd ? self::parseClock($end) : self::DAY_END;

        if (null === $startMinute || null === $endMinute || $startMinute >= $endMinute) {
            return null;
        }

        return new self($startMinute, $endMinute);
    }

    private static function parseClock(string $value): ?int
    {
        if (1 !== preg_match('/^([01]\d|2[0-4]):([0-5]\d)$/', $value, $matches)) {
            return null;
        }

        $minutes = (int) $matches[1] * 60 + (int) $matches[2];

        return $minutes > self::DAY_END ? null : $minutes;
    }

    public function isAllDay(): bool
    {
        return self::DAY_START === $this->startMinute && self::DAY_END === $this->endMinute;
    }

    /**
     * Half-open overlap: 09:00-13:00 and 13:00-17:00 do NOT collide.
     */
    public function overlaps(self $other): bool
    {
        return $this->startMinute < $other->endMinute && $other->startMinute < $this->endMinute;
    }

    public function equals(self $other): bool
    {
        return $this->startMinute === $other->startMinute && $this->endMinute === $other->endMinute;
    }

    public function start(): string
    {
        return self::format($this->startMinute);
    }

    public function end(): string
    {
        return self::format($this->endMinute);
    }

    public function __toString(): string
    {
        return $this->isAllDay() ? 'ganztägig' : $this->start().'–'.$this->end();
    }

    private static function minutesOf(\DateTimeInterface $time): int
    {
        return (int) $time->format('G') * 60 + (int) $time->format('i');
    }

    private static function format(int $minutes): string
    {
        return \sprintf('%02d:%02d', intdiv($minutes, 60), $minutes % 60);
    }
}